258 C. LAPWOKTH ON THE MOFFAT SERIES. 



contact with the greywackes at both ends of the section are identical, 

 although they dip in the same direction, it is clear that we have here 

 a faulted anticline or syncline, the axis of which is inverted. 



(c) Description of the Section along line C-D. 

 (Plate XII. Sect. II.) 



This section crosses the Main Cliff near its southern extremity, at 

 right angles to its general direction. Its western half is made up 

 of the strata enumerated in our typical section, and the total expo- 

 sure of the Moffat Shales along its course is reduced to a little more 

 than half the diameter of that on our former traverse. 



Commencing at the summit of the Main Cliff, the coarse greywackes 

 of the falls are seen dipping at a gentle angle to the west, off the 

 Grey-shale group ; and, descending the line of section, the various 

 strata of the Birkhill, Hartfell, and Glenkiln divisions, as tabulated, 

 are passed over in orderly succession. Thrust abruptly against the 

 patch of Glenkiln Shales in the southern angle of the cliff, and 

 dipping generally in the same direction, are some contorted grey and 

 black bands yielding a few fragments of Birkhill forms. These be- 

 come more numerous in some bosses of hard, flaggy, and contorted 

 black shale, through which the stream cuts its passage, and include 

 D. vesiculosus, D. tamariscus, and M. gregarius. The presence of 

 some nodular and coloured clay bands at this spot are an additional 

 evidence that these beds belong mainly to the M.-gregarius zone. This 

 is at once proved to be the case if we follow them in their course 

 along the east bank of the stream to the northward, where in a 

 naked portion of the East Cliff, a short distance below the foot of 

 the Long Burn, they are exhibited in a magnificent exposure. Every 

 characteristic of the M.-gregarius zone is here apparent, the large 

 central nodule-band being especially conspicuous among the con- 

 torted strata, and the special fossils obtainable in great profusion. 



Between this contorted zone (which is visibly the southerly con- 

 tinuation of the contorted M.-gregarius zone of our former section) 

 and the wedge of Glenkiln Shales at the foot of the East Cliff must 

 therefore be a fault cutting out the whole of the Hartfell Shales. A 

 glance at the map (PL XL) will show that this is the southerly continua- 

 tion of the main fault of the North Cliff detected in our former section. 



Beposing upon this contorted M.-gregarius zone, and passing 

 below the greywackes that form the higher portion of the East Cliff, 

 are the grey and black bands of the Upper Birkhill Series. They are 

 exposed only in fragmentary patches in some of the numerous scores 

 that furrow the talus-covered slope ; but, as already mentioned, the 

 zones of M. Sedgwicki and M. cometa are plainly discernible, and the 

 characteristic white-clay bands may be detected everywhere among 

 them on clearing away the overlying debris. 



Thus on both sides of this section the thick barren greywackes 

 and flagstones of the surrounding country are the highest beds, and 

 they are in both cases immediately underlain by the Grey- shale 

 group of the Birkhill Shales, which in its turn is supported by the 

 nodular or M.-gregarius zone. 



